Conventionally humidity sensors wherein a humidity-sensitive film has been interposed between two electrodes have been known as sensors of this type. (See, for example, Japanese Unexamined Patent Application Publication H6-94663 (“JP '663”).) In this type of humidity sensor, the electrostatic capacitance value of the humidity-sensitive film varies in accordance with the humidity within the measurement environment. Because of that, it is possible to convert (calculate) the detected electrostatic capacitance value into a humidity level if the correspondence relationship between the humidity and the electrostatic capacitance value is known in advance.
Moreover, in addition to environment sensors of an electrostatic capacitance type, described in JP '663, there are also known environment sensors for detecting physical quantities in the environment using methods such as a heat type, an optical type, a chemical type, and an electrical type.
Note that in these conventional environment sensors, typically the amount of electrical power assumed has not been an issue because they have been supplied electrical power from so-called fixed power supplies. However, in recent years there has been an increasing need to detect physical quantities in a variety of different environments, and it has been desirable to reduce the amount of power consumed by the environment sensor in devices wherein there are limitations to the amount of power from the power supply, such as in mobile or portable devices.
Several situations for the present examples have been considered for the problem set forth above, and one object is to provide an environment sensor able to reduce the amount of power consumed.